The present invention relates to managing computer data, and more specifically to managing data replication.
It is common for a storage system to have one or more of its disks backed up at a remote location to allow for disaster recovery. Most storage systems support simple point-to-point remote replication, from one source disk to one target disk, although some enterprise systems do support three-site replication. The replications may be performed in a synchronous or asynchronous manner.
In synchronous replication, the source storage system does not report completion of an operation (e.g., a write) until the target storage system has completed the operation. Thus, while guaranteeing an identical copy of a disk, this process is relatively slow and typically forces the target disk to be located relatively near the source disk.
In asynchronous replication, the source storage system can report completion of an operation before the target storage system has completed the operation (e.g., upon receiving notice that the target storage system has received the communication conveying the operation). Thus, this process is relatively fast and allows the target disk to be located farther away from the source disk, but does not guarantee an identical copy of the disk.